Script to generate CouchDB authentication cookie with expiration period of one year

main.go

package main

import (
	"bytes"
	"crypto/hmac"
	"crypto/sha1"
	"encoding/base64"
	"flag"
	"fmt"
	"os"
	"strings"
	"time"
)

func main() {
	var user = flag.String("user", "", "username")
	var secret = flag.String("secret", "", "global secret")
	var salt = flag.String("salt", "", "user's salt")

	flag.Parse()

	for argName, arg := range map[string]*string{"user": user, "secret": secret, "salt": salt} {
		if *arg == "" {
			fmt.Printf("%s is required paramter!\n", argName)
			os.Exit(1)
		}
	}

	expiration := time.Now().Add(8760 * time.Hour).Unix()

	msg := []byte(fmt.Sprintf("%s:%X", *user, expiration))
	key := []byte(*secret + *salt)
	mac := hmac.New(sha1.New, key)
	mac.Write(msg)
	control := mac.Sum(nil)

	cookieRaw := bytes.Join([][]byte{msg, control}, []byte(":"))

	cookie := base64.StdEncoding.EncodeToString(cookieRaw)

	// Don't ask. CouchDB is very... unique in how it does base64 encoding
	cookie = strings.TrimRight(cookie, "=")
	cookie = strings.ReplaceAll(cookie, "/", "_")
	cookie = strings.ReplaceAll(cookie, "+", "-")

	fmt.Printf("#HttpOnly_127.0.0.1\tFALSE\t/\tFALSE\t%d\tAuthSession\t%s\n", expiration, cookie)
}

reverse.go

package main

import (
	"bytes"
	"crypto/hmac"
	"crypto/sha1"
	"encoding/base64"
	"flag"
	"fmt"
	"os"
	"strconv"
	"strings"
	"time"
)

func main() {
  var user = flag.String("cookie", "", "cookie")
	var secret = flag.String("secret", "", "global secret")
	var salt = flag.String("salt", "", "user's salt")

	flag.Parse()
  
	cookieRaw, _ := base64.StdEncoding.DecodeString(*cookie)

	attr := bytes.Split(cookieRaw, []byte(":"))

	fmt.Printf("name: %q\n", attr[0])

	expiration, _ := strconv.ParseInt(string(attr[1]), 16, 64)
	fmt.Printf("expiration: %d\n", expiration)

	key := []byte(*secret + *salt)
	msg := bytes.Join([][]byte{attr[0], attr[1]}, []byte(":"))

	mac := hmac.New(sha1.New, key)
	mac.Write(msg)
	control := mac.Sum(nil)

	fmt.Printf("returned hmac  : %#v\n", attr[2])
	fmt.Printf("calculated hmac: %#v\n", control)
}